Mortality-related immune features and COVID-19

To the Editor:

We would like to share ideas on the report “Predictive nomogram for severe COVID-19 and identification of mortality-related immune features.”¹ Cai et al¹ noted that “the abundance of CD45RO⁺CD3⁺ T cells and neutrophil-to-lymphocyte and neutrophil-to-natural killer cell ratios may serve as useful prognostic predictors in severe patients.” The finding from this small study is interesting. Indeed, the change in white blood cells in coronavirus disease 2019 (COVID-19) is possible and might contribute to the clinical manifestations.² Several factors can additionally contribute to the severity of infection. The underlying disease of the patient might also be reactivated because of COVID-19. Nevertheless, as noted by Lupia et al,³ there is a role of cytokine response during COVID-19 illness that is an important determinant for severity, and the clinical problem due to change in white cells might be overt during the recovery stage of COVID-19 when there is a decreased level of cytokine response.